From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754223AbaEECUG (ORCPT ); Sun, 4 May 2014 22:20:06 -0400 Received: from ozlabs.org ([103.22.144.67]:39676 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754018AbaEECUC (ORCPT ); Sun, 4 May 2014 22:20:02 -0400 From: Rusty Russell To: Andrew Morton Cc: Linus Torvalds , Mateusz Guzik , Greg Kroah-Hartman , Steven Rostedt , LKML , Thomas Gleixner , "H. Peter Anvin" , Borislav Petkov , Ingo Molnar , Mel Gorman , Kay Sievers Subject: Re: [RFC PATCH] cmdline: Hide "debug" from /proc/cmdline In-Reply-To: <20140502153409.329d3b5b426275e8197251a2@linux-foundation.org> References: <20140402144219.4cafbe37@gandalf.local.home> <20140402221212.GD16570@mguzik.redhat.com> <87wqf1oi22.fsf@rustcorp.com.au> <20140502153409.329d3b5b426275e8197251a2@linux-foundation.org> User-Agent: Notmuch/0.17 (http://notmuchmail.org) Emacs/24.3.1 (x86_64-pc-linux-gnu) Date: Mon, 05 May 2014 11:47:22 +0930 Message-ID: <871tw9c6kt.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton writes: > On Mon, 07 Apr 2014 14:24:45 +0930 Rusty Russell wrote: > >> Subject: param: hand arguments after -- straight to init >> >> The kernel passes any args it doesn't need through to init, except it >> assumes anything containing '.' belongs to the kernel (for a module). >> This change means all users can clearly distinguish which arguments >> are for init. >> >> For example, the kernel uses debug ("dee-bug") to mean log everything to >> the console, where systemd uses the debug from the Scandinavian "day-boog" >> meaning "fail to boot". If a future versions uses argv[] instead of >> reading /proc/cmdline, this confusion will be avoided. >> >> eg: test 'FOO="this is --foo"' -- 'systemd.debug="true true true"' >> >> Gives: >> argv[0] = '/debug-init' >> argv[1] = 'test' >> argv[2] = 'systemd.debug=true true true' >> envp[0] = 'HOME=/' >> envp[1] = 'TERM=linux' >> envp[2] = 'FOO=this is --foo' > > This (user-facing) feature doesn't seem to have been documented > anywhere. Documentation/kernel-parameters.txt, I guess. That document does need some love. How's this? 1) __setup() is messy, prefer module_param and core_param. 2) Document -- 3) Document modprobe scraping /proc/cmdline. 4) Document handing of leftover parameters to init. 5) Document use of quotes to protect whitespace. diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 43842177b771..56a4c2d0c741 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1,27 +1,37 @@ Kernel Parameters ~~~~~~~~~~~~~~~~~ -The following is a consolidated list of the kernel parameters as implemented -(mostly) by the __setup() macro and sorted into English Dictionary order -(defined as ignoring all punctuation and sorting digits before letters in a -case insensitive manner), and with descriptions where known. - -Module parameters for loadable modules are specified only as the -parameter name with optional '=' and value as appropriate, such as: - - modprobe usbcore blinkenlights=1 - -Module parameters for modules that are built into the kernel image -are specified on the kernel command line with the module name plus -'.' plus parameter name, with '=' and value if appropriate, such as: - - usbcore.blinkenlights=1 +The following is a consolidated list of the kernel parameters as +implemented by the __setup(), core_param() and module_param() macros +and sorted into English Dictionary order (defined as ignoring all +punctuation and sorting digits before letters in a case insensitive +manner), and with descriptions where known. + +The kernel parses parameters from the kernel command line up to "--"; +if it doesn't recognize a parameter and it doesn't contain a '.', the +parameter gets passed to init: parameters with '=' go into init's +environment, others are passed as command line arguments to init. +Everything after "--" is passed as an argument to init. + +Module parameters can be specified in two ways: via the kernel command +line with a module name prefix, or via modprobe, eg: + + (kernel command line) usbcore.blinkenlights=1 + (modprobe command line) modprobe usbcore blinkenlights=1 + +Parameters for modules which are built into the kernel need to be +specified on the kernel command line. modprobe looks through the +kernel command line (/proc/cmdline) and collects module parameters +when it loads a module, so the kernel command line can be used for +loadable modules too. Hyphens (dashes) and underscores are equivalent in parameter names, so log_buf_len=1M print-fatal-signals=1 can also be entered as log-buf-len=1M print_fatal_signals=1 +Double-quotes can be used to protect spaces in values, eg: + param="spaces in here" This document may not be entirely up to date and comprehensive. The command "modinfo -p ${modulename}" shows a current list of all parameters of a loadable